1. Field of the Invention
The invention relates to a light guide member and a backlight unit including a light guide member. More particularly, the invention relates to a light guide member for guiding light traveling therein and providing uniformly distributed light, and a backlight unit employing such a light guide member.
2. Description of the Related Art
A light guide member may be employed, e.g., by an illumination device of a display device, to receive light from a light source of the illumination device and guide the received light so as to provide light having a uniform luminance distribution to a display panel of the display device. For example, a flat panel display device, e.g., a liquid crystal display (LCD), may include an illumination device, e.g., a backlight unit (BLU), which may include a light guide member.
There is a demand for improved display devices in, e.g., the information and communication industries. More particularly, e.g., higher resolution, lighter, thinner, and/or less power consuming display devices are desired. One possible approach for developing such improved display devices is to provide thinner, lighter BLUs and/or improved light guide members capable of providing light having a more uniform luminance distribution.
For example, one type of flat panel display that is widely used today is thin film transistor-liquid crystal displays (TFT-LCDs). Such TFT-LCDs may include a LCD panel in which liquid crystal is provided between two substrates, a BLU as an illumination device positioned in a lower portion of the LCD panel, and a LCD drive IC (LDI) for driving the LCD panel. The BLU unit may include, e.g., a light source, a light guide member, and an optical sheet including a diffusion sheet and a prism sheet.
The light source may supply non-uniformly distributed linear light to the light guide member. Generally, the light guide member is to modify the non-uniformly distributed linear light and output planar light having a uniform optical distribution. However, conventional light guide members fall short of outputting uniformly distributed linear light. For example, portions of the light guide member arranged between, and in close proximity to, light sources of the illumination device may provide less light, i.e., appear darker, than portions of the light guide member arranged substantially along a zero-degree radiation angle of the respective light source.
More particularly, in general, as the radiation angle of light from the light source increases, light intensity decreases. The diffusion of light is also generally weak at a portion of a light guide member close to the light source. Thus, e.g., at portions of the light guide member receiving light from the light source via relatively larger radiation angles and/or beyond a radiation angle of the light, the intensity of light output from the light guide member may not have a uniform luminance distribution. As a result of such non-uniformity, a luminance distribution of light from the light guide member may include a bright line, bright area and/or dark area close to the light source, i.e., a bright line/area effect. FIG. 1 illustrates a photograph of a brightness distribution of a conventional light guide member 31. As may be seen from FIG. 1, as a result of the bright line/area effect, a dark portion A exists between light sources 32. Such a bright line/area effect may be particularly prominent at portions of the light guide member that do not overlap with or are not aligned with light sources of a light source unit. When light having a non-uniform luminance distribution is provided to a display device, image quality of the display device may be hindered.
In view of such shortcomings of the light guide member, a BLU employing such light guide members may include a plurality of optical sheets, e.g., a diffusion sheet and a prism sheet, in an attempt to provide light having a more uniformly distributed luminance to the display device. However, having to provide additional optical sheets may increase, e.g., the cost, weight and/or size of the BLU.